A known technique for separating constituents A and B in solution in a liquid mixture consists in injecting the latter into a chromatography column subjected to a centrifugal force, intended to allow one of the liquid phases to be percolated in the other liquid phase and vice versa (CCC or CPC chromatography).
In practice, as shown notably in patents FR-2,791,578, U.S. Pat. No. 4,877,523 or U.S. Pat. No. 4,857,187, this type of chromatography system comprises one or more stacks of discs driven into rotation. Each one comprises in the thickness thereof and over the entire periphery thereof a succession of cells arranged in a radial or oblique direction and connected in series by a set of circuits of fine winding channels at the ends of each cell. The circuits of all the discs communicate with one another. The cells and their communication circuits are filled with a stationary liquid phase kept in place by the centrifugal force and another mobile liquid phase that percolates the stationary phase.
Rotation of the stack creates a high centrifugal acceleration field that allows to keep in place the liquid phase referred to as fixed stationary phase, whereas the mobile phase circulates in ascending mode if it is lighter than the stationary phase, and in descending mode if it is heavier.
Separation of the constituents of a feed in liquid solution consisting of at least two constituents having different partition coefficients, such that they are entrained at unequal velocities by the mobile phase that can be one or the other of the liquid phases, is carried out in this type of device consisting of the interconnection in series of one or more chains of cells.
The chromatographic process, i.e. partition of the molecules to be purified between the two liquid phases, takes place in each cell, and mass transfer is favoured by a good dispersion of the mobile phase coming from the channel in each cell.
A first and double drawback of this prior art is due to the design of the cells driven through the thickness of the discs, which requires seals, generally flexible, made of Teflon par example, between each disc, thus closing each cell along the plane of the disc, therefore perpendicular to the main axis of each cell. Even if the cell has rounded shapes to facilitate dispersion homogeneity for a better matter exchange between the two phases, the bond lines create with the cell right angles that are not favourable to homogeneous dispersion of the liquids. Finally, these flexible bond lines subjected to continuous liquid pressure variations deform over time and they modify the geometry of the cells, hence aging of the device.
A second drawback lies in that the cells are connected to each other by a ribbon-shaped channel. It can be readily calculated and checked that this line shape, for a given section, produces a pressure drop that is much higher than that caused by a line of same section, but square or cylindrical. In order to limit too high pressures and, in some cases, for machining difficulty reasons, the thickness of these lines has to be increased, thus increasing the dead volumes in which the products being separated partly mix again, which reduces the efficiency and the productivity of the device. Furthermore, if the thickness of the line is not perfectly constant over the entire length thereof, which is the case when the cells are water jet cut, a gradient of the velocity vectors of the mobile liquids (phase and compounds to be separated) appears between one face of the disc and the other, which tends to spread the compounds that are being separated, therefore to remix them and consequently to reduce the efficiency and productivity performances of the machine.